Method and apparatus for spinning and stretching viscose rayon



METHOD AND APPARATUS FOR SPINNING AND STRETCHING VISCOSE RAYON F. HILDEBRANDT ETAL Filed June 27, 1958 Oct. 31, 1961 mI I'ILN'IH INVENTORS: FRIEDRICH HILDEBRANDT HEINZ HOSE BY ATT'YS many Filed June 27, 1958, Ser. No. 744,960 3 Claims. (Cl. 188) This invention relates to an improved method and apparatus for spinning and stretching viscose rayon, i.e. a filamentary material obtained by regenerating cellulose from a viscose spinning solution in order to produce an especially uniform and strong staple fiber. In particular, the invention is concerned with the specific method of producing viscose staple fibers wherein the viscose spinning solution is first extruded or spun into an acid coagulating bath in which the precipitating filaments are only partially regenerated and stretched, followed by a subsequent stretching and further regeneration or decomposition in a second stretching bath. It is the main object of this invention to provide an improved method and corm bination of apparatus for the application of this second regenerating and stretching bath.

The viscose process for spinning and stretching regenerated cellulose filaments is well known, and many alternative methods have been suggested in the art for obtaining particular physical properties and characteristics in the finished product. Where the extruded filaments are subjected to treatment by two baths, no problem arises with respect to the first acid coagulating bath since it need act for only a short period of time upon the filaments, but it has been an especially ditficult problem to treat the filaments in a second regenerating bath while simultaneously stretching the filaments therein. The

filaments must remain in the second bath for a relatively 7 longer period of time since the regeneration of the cellulose therein is adapted to proceed more slowly. In addition, when spinning tows for the production of staple fiber it is difiicult to avoid the filaments being entangled. Therefore, they are preferably conducted through the bath in such a manner as to completely and uniformly wet the individual fibers or filaments so that the use of thick and closely intertwined or woven tows or threads containing a large number of filaments must be avoided.

Thus, in attempts to completely immerse or submerge the filaments in the second regenerating and stretching bath, space requirements dictate that the filaments travel between the feed and draw rolls around a large number of guide or filament deflecting rollers which must also be submerged in the bath. These rollers operating within the bath are difficult to maintain in satisfactory order because of corrosion by the bath, and improper mountings or seatings of the rollers lead to an impairment of the spinning and stretching process. These problems can be avoided if the filaments are conducted horizontally between the feed and draw rolls and the second bath then sprayed upon the horizontal filaments. However, such spraying must be limited to only a small number of filaments which can only contact the bath liquid for a short and inadequate period of time. The same applies to filaments being drawn horizontal-1y through this bath while they are being submerged. However, very often troubles occur due to the high friction which the filaments suffer especially at high drawing off speeds. The length of the filaments upon which the bath is sprayed or which are drawn through the bath can, of course, be arbitrarily increased, but in this case much greater space is required and there is a considerable loss of spinning capacity. Moreover, due to different lengths of the ways which the filaments have to travel before the second bath the degrees of decomposition and, consequently, the stretching are different and, therefore, the qualities of the filaments are impaired.

One object of the present invention is to provide an improved method and apparatus for spraying a second hot bath liquid upon extruded and partially regenerated cellulose filaments whereby high spinning capacity can be maintained, and, at the same time, corrosion or other damage to filament handling elements can be avoided.

Another object of the invention is to provide an im-,- proved method and apparatus for spinning and stretching viscose rayon filaments such that a greater operating flexibility can be attained in the combination of an acid coagulating bath with a second stretching bath.

Yet another object of the invention is to provide an improved method and apparatus wherein the conditions under which a second stretching bath is applied to cellulose filaments can be varied and controlled to give dilferent characteristics to viscose staple fibers.

Still another object of the invention is to provide an improved method and apparatus to ensure equal times of treatment and equal conditions for all filaments and thus to obtain especially uniform and strong staple fibers.

These and similar objects and advantages will become more obvious upon consideration of the following detailed disclosure of the invention taken in conjunction with the accompanying drawing which illustrates a preferred apparatus in accordance with the invention in a schematic perspective view.

With the present invention, it has now been found that the spinning and stretching of viscose rayon filaments can be greatly improved when employing a first acid coagulating bath followed by additional stretching and regeneration of cellulose in a second hot liquid bath if the filaments are collected from the first bath as a single wide band of closely associated filaments, and this wide band conducted vertically between a feed roll means and draw roll means in order to stretch the filaments while simultaneously spraying the second bath on both sides of the vertically positioned wide band. In this manner, the hot bath liquid flows downwardly on the filaments and is maintained in intimate contact with them. The second bath, like the first bath, is an acid aqueous composition or solution capable of regenerating cellulose from the extruded and coagulated viscose. The filaments are preferably initially extruded in the acid coagulating bath as a plurality of wide bands by means of so-called wide beam spinnerettes for convenient collection into a single wide and relatively narrow band of closely packed or accumulated filaments. It is most advantageous to locate the feed and draw roll means for the second bath imme diately above the spinnerettes or spinning heads in the first bath and to permit the hot bath liquid sprayed upon the filaments to flow downwardly between the feed and draw rolls in a direction countercurrent to an upward vertical travel of the filaments.

Referring now to the drawing, four wide beam spinnerettes or spinning heads 1 are spaced a short distance apart in an acid coagulating bath 2 which coagulates and partially regenerates the freshly spun viscose solution in the form of a plurality of filaments. The spinning orifices in the wide spinnerettes 1 are arranged within an elongated narrow zone such that a wide and relatively narrow band of filaments 3 is extruded upwardly from each spinnerette or spinning head. Each of these wide bands 3 is then collected by means of guide rollers 4 and the triangular liquid stripping elements 5 into a single wide band 6 of closely associated and partially stretched filaments. The stripper 5 also serves to remove any excess liquid from the coagulating or precipitating bath 2 carried upwardly with the filaments. The individual filaments in the wide band 6 are then simultaneously stretched and further regenerated in a second bath by conducting the wide band first around feed roll means, including the large roller or drum 8 and the smaller rollers 7a, 7b and 7c, and then vertically upwardly around draw roll means, including the large cylinder 9 and smaller rollers 10a and 10b. The smaller rollers 7a, 7c and 10a act as filament or band deflecting r guiding means while the feed drum 8 and its small roller 7b and the drawing cylinder 9 and its smaller roller 10b are positively driven as indicated by the arrows and impart a forward motion to the filaments or band 6. The filaments are thus stretched between the feed roll means and draw roll means in a conventional manner by suitably adjusting the speeds of the rolls. In the particular apparatus shown in the drawing, the feed roll means, i.e. drum 8 and its associated elements, also act to draw off the freshly spun or extruded filament bands 3 at a predetermined speed so as to partially stretch the filaments.

The second bath is applied to the vertically positioned wide band of filaments 6 as stretching is accomplished be tween the feed and draw roll means. At least one pair of oppositely disposed spray nozzles 11 supplied by conduit 12 is located laterally with respect to and near the top of the vertically moving band 6 so that a hot bath liquid can be sprayed on both sides of? the filamentary band. A second set of stripping elements 13 is positioned just above the spray nozzles to remove excess bath liquid and to prevent the liquid from being carried along with the filaments. With this arrangement, the liquid of the second bath runs or flows downwardly so as to uniformly envelope and intimately contact the filaments.

It is especially important for the bath liquid to flow downwardly in a countercurrent direction to the upward travel of the filaments in that the liquid is to be held on the band of filaments throughout its vertical travel and the filaments are to be progressively regenerated while being continuously brought into contact with fresh bath liquid at the point of greatest regeneration of the cellulose. Where a hot bath liquid is employed, it will tend to cool during its downward travel upon the filaments, thereby contributing to a progressive regeneration. Excess bath liquid is collected in -a trough or similar vessel 14 as the band 6 passes around 70, and the recovered liquid is led off by conduit 15 and preferably recycled by any suitable means (not shown) over a tank inwhich the bath is adjusted, back to the spray nozzles 11. This system is very economical with respect to the quantity of bath liquid which is required. In addition, the concentration and the temperature of the bath can be kept completely uniform which is important for the high strength of the fibers required.

The particular arrangement of the second stretching and regenerating zone vertically over the group of spinning heads or spinnerettes permits a concentration of a very high spinning output in a comparatively small space. Each of the individual elements in the apparatus is conventional in its construction, and it is the combination and arrangement of these elements which constitute the intended improvement. The drawing merely indicates one embodiment of the invention and is not exclusive since those skilled in the art can readily substitute various well known elements having an equivalent function without departing from the spirit and scope of the novel com.- bination.

Several units of the arrangement described are united to a spinning machine, eg 4 to 25 units.

Although the method and apparatus of the invention are generally applicable to any of the known viscose processes requiring the use of two regenerating baths accompanied by stretching, especially good results have been obtained under the preferred conditions set forth hereinafter and illustrated by a subsequent example. Percentages and parts are by weight unless otherwise indicated.

The viscose spinning solution may have any composition which will depend on the nature of the fibers to be spun. It may have e.g. a cellulose content of about 7 to 10% and an alkali content based upon sodium hydroxide of about 5 to 8%. Other conventional additives can also be contained in the spinning solution.

The number of filaments being treated and stretched together depends on the individual denier of the filaments which may vary between 1 and 20 denier. As a rule, the total denier of the band should not exceed 40,000, i.e. the band may consist e.g. of 40,000 filaments of 1 denier each, or 2,000 filaments of 20 denier each, or 20,000 filaments of 1.5 denier each, or 6,000 filaments of 6 denier each and so on. After leaving the acid coagulating bath the filaments are most advantageously collected into a single wide band of closely abutting filaments so that the band is thin having only very few layers of filaments, the number of layers increasing, of course, with a rising number of filaments.

The first acid coagulating bath should be made up into an aqueous composition as follows: sulfuric acid 7 to 15%; sodium sulfate 25 to 35%; and zinc sulfate 1 to 5%. Other well know ingredients can be employed in the first bath. Lauryl pyridinium sulfate is often advantageously used in a quantity of about 3 to 5 mtg/liter. This bath is preferably maintained at a temperature of about 40 to 60 C. It will be understood, of course, that the above conditions are so correlated Within the specified ranges and the filaments contacted with the acid coagulating bath for a period of time such that only a partial regeneration and stretching of the filaments occurs.

The second bath sprayed upon the vertically positioned Wide band of filaments is also an acid aqueous composition maintained at a temperature of about to 99 C. as it is being sprayed. The pressure or force of the liquid being sprayed is preferably between about 0.5 and 4. atmospheres. The second bath generally contains the same ingredients as the first coagulating bath, but in a smaller concentration, e.g., about 8 to 15% of the concentration of the coagulating bath. In this way, both baths can be mixed together at the concentration of the first bath and a portion taken off and diluted with water for use in the second bath.

The distance between the top of the second bath to the lower end thereof at which the liquid is drained ofl is most advantageously about 1,500 mm. Because of the stretch to be applied between them the feed roller and the draw roller have a difierent speed. The filaments are drawn off by the draw roller with a speed of 20 to 100 meters per minute and the stretch in this second bath may be up to about 100%, preferably between about 20 and 40%.

The above conditions can be varied with a very accurate control upon the desired characteristics to be imparted to the fibers. The progressive regeneration which takes place in the second bath because of the counterourrent flow of the bath to the direction of filament travel is especially helpful in obtaining uniform and highly beneficial fiber properties. The vertical bath can be further modified by the use of additional pairs of spray nozzles of varying temperatures and acid content located at any point in the vertical travel of the filaments so as to obtain any desired degree of regeneration with respect to percentage stretch. These and other modifica- 'tions will be apparent to those skilled in the art.

After the second stretching bath, the filaments, together with those of the other bands from the same spinning machine will be preferably cut into staple fibers which are subsequently washed and further treated in accordance with accustomed practice, e.g., for crimping, application of finishing agents, and the like. The conversion into staple fiber may, if desired, take place at the end of the chemical treatment.

The following example servesbto give a specific illustration of one preferred method of practicing the present invention, but the invention is not to be limited to this example.

Example 1 (Measured with a steel ball of diameter over 200 mm. at 20 C.)

The filaments had a length of travel of approximately 30 cm. in this first bath the temperature of which was maintained at 47 C. This bath had the following composition:

Sulfuric acid grams/liter 115 Lauryl pyridinium sulfate mg./liter 4 Zinc sulfate grams/1iter 11 Specific weight 1.300

The filaments were then collected into a single wide band and conducted vertically between a set of feed and draw roll means with the simultaneous spray application of the second bath. The speeds of the feed and draw rolls were adjusted to obtain a stretching of 30%, the circumferential speed of the draw roll being 60 m./min. The vertical bath zone had a length of approximately 15 meters, i.e. between the point at which the bath is applied near the top of the vertical zone and the bottom thereof where the bath liquid is recovered. The second bath was applied through a pair of oppositely disposed and horizontally positioned spray nozzles at a temperature of 93 C. and at a rate of 60 liters/minute. Excess bath liquid withdrawn at the bottom of the vertical zone was recovered, reheated, readjusted and recycled to the spray nozzles. This second bath consisted of an aqueous solution identical to the first bath but diluted to of the original concentration shown above.

The resulting filaments had a denier of 1.5, tensile strength of 3 grams/denier (dry) and an elongation of 19% (dry). They exhibited very excellent uniform properties and could be easily crimped or otherwise treated to obtain desired textile properties.

The foregoing improved method and apparatus of the invention are admirably suited for a careful quality control and high output of viscose rayon filaments. By means of the vertical arrangement of the second bath zone over the first spinning and coagulating bath, an economy of space is effected and the length of the second bath zone is itself maintained within easily managed limits. The method is quite versatile so that opcrating conditions can be changed rapidly and at the same time controlled to obtain preferred fiber characteristics in the finished product.

The invention is hereby claimed as follows:

1. In a combination of apparatus for the production of viscose rayon requiring two separate baths for stretching and regenerating cellulose filaments from a viscose spinning solution, the improvement which comprises: means to extrude a plurality of filaments of viscose into a first acid coagulating bath; guide means to collect said plurality of filaments into a wide band of closely associated filaments; a feed roll means and a guide roll means arranged vertically with respect to each other which engage and vertically transport and stretch said filaments in a wide band; at least one pair of oppositely disposed spray nozzles arranged near the top of said wide band between said feed and draw roll means, said nozzles being located to spray a hot bath liquid against said wide band of filaments so that the bath liquid flows downwardly on the filaments; and means to collect the bath liquid near the lower end of said wide band between said feed and draw roll means.

2. An improved apparatus in combination as claimed in claim 1 wherein said means to extrude a plurality of filaments includes at least one wide beam spinnerette in which a plurality of spinning orifices are arranged within an elongated narrow zone for extrusion of a wide band of filaments.

3. In a method of spinning and stretching regenerated cellulose filaments by the viscose process wherein the extruded filaments are subjected to a first acid coagulating bath followed by additional regeneration and stretching in a second coagulating bath, the improvement which comprises: collecting the extruded filaments from the first acid coagulating bath as a single wide band of closely associated filaments; conducting said wide band of filaments in an upward and vertical direction between a feed roll and a draw roll; stretching said filaments between said feed roll and said draw roll and simultaneously spraying a second bath of coagulating liquid on both sides of said vertically positioned and upwardly moving band of filaments, said spray being applied to both sidesof said band at a point between said feed roll and said draw roll such that the hot liquid of the bath flows downwardly on the filaments, whereby said filaments are stretched and further regenerated.

References Cited in the file of this patent UNITED STATES PATENTS 2,210,116 Dreyfus Aug. 6, 1940 2,265,984 Allen et al. Dec. 16, 1941 2,317,152 Costa Apr. 20, 1943 2,334,325 Heim Nov. 16, 1943 2,536,094 McDermott Jan. 2, 1951 2,566,457 Levison et al. Sept. 4, 1951 2,611,929 Hoxie Sept. 30, 1952 2,788,256 Allen Apr. 9, 1957 2,898,627 Bley Aug. 11, 1959 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No 3,OO6 O27 October 31 1961 Friedrich Hildebrandt et al0 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the heading to the printed speciificatiom between lines 8 and 9, insert the following:

Claims priority application Germany June 29 1957 Signed and sealed this 24th day of April 1962B (SEAL), Attestz- ESTON Ga JOHNSON DAVID L LADD Attesting Officer Commissioner of Patents 

1. IN A COMBINATION OF APPARATUS FOR THE PRODUCTION OF VISCOSE RAYON REQUIRING TWO SEPARATE BATHS FOR STRETCHING AND REGENERATING CELLULOSE FILAMENTS FROM A VISCOSE SPINNING SOLUTION, THE IMPROVEMENT WHICH COMPRISES: MEANS TO EXTRUDE A PLURALITY OF FILAMENTS OF VISCOSE INTO A FIRST ACID COAGULATING BATH, GUIDE MEANS TO COLLECT SAID PLURALITY OF FILAMENTS INTO A WIDE BAND OF CLOSELY ASSOCIATED FILAMENTS, A FEED ROLL MEANS AND A GUIDE ROLL MEANS ARRANGED VERTICALLY WITH RESPECT TO EACH OTHER WHICH ENGAGE AND VERTICALLY TRANSPORT AND STRETCH SAID FILAMENTS IN A WIDE BAND, AT LEAST ONE PAIR OF OPPOSITELY DISPOSED SPRAY NOZZLES ARRANGED NEAR THE TOP OF SAID WIDE BAND BETWEEN SAID FEED AND DRAW ROLL MEANS, SAID NOZZLES BEING LOCATED TO SPRAY A HOT BATH LIQUID AGAINST SAID WIDE BAND OF FILAMENTS SO THAT THE BATH LIQUID FLOWS DOWNWARDLY ON THE FILAMENTS, AND MEANS TO COLLECT THE BATH LIQUID NEAR THE LOWER END OF SAID WIDE BAND BETWEEN SAID FEED AND DRAW ROLL MEANS. 